Fallback plan:
If anything goes wrong, I guess the only important thing changed are the .list files.
The script creates a backup for each .list file, for example /etc/apt/sources.list.d/test.list
is backed up as /etc/apt/sources.list.d/test.list.backup

Re: Update your Launchpad PPA repositories and apt keys

I've moved this to General Help from Tutorials & Tips. My reasoning is that this is really just a script that does everything for you. Scripts updating repositories especially are generally discouraged, because if it fails then the user is left with an unusable system save for the backup list.

You are free to resubmit your tutorial, but please make sure that it details how a user can update their sources and add GPG keys, don't just do it for them with a script.